1. Field of the Invention
The present invention relates to power tools, such as those used for trimming and grooving wooden workpieces.
2. Description of the Related Art
Power tools known as trimmers and routers have been used for trimming or grooving wooden workpieces. In general, this kind of power tools includes a base device and a tool unit that is also called a motor unit. The base device is adapted to contact with a workpiece, and may be placed on a workpiece. The tool unit is supported by the base device with the tool unit being positioned relative to the base device. Due to positioning of the tool unit relative to the base, the tool unit can be also positioned relative to the workpiece with which the base device contacts. The tool unit has a drive motor disposed therein for rotatably driving a spindle. A tool bit may be mounted to the spindle for machining a workpiece. A plurality of tool bits may be prepared for selectively mounted to the spindle depending a machining work to be performed.
The drive motor is disposed within a housing of the tool unit. The housing serves as an enclosure. Therefore, the housing is positioned relative to the workpiece while it serves as an enclosure for the drive motor. Various techniques relating to these functions are disclosed, for example, in Japanese Laid-Open Patent Publications Nos. 2002-234001 and 2002-337073.
The housing of the tool unit may be formed of synthetic resin for ensuring insulation of the drive motor and the other electric components disposed within the housing. However, there is a possibility that the resin molded housing is deformed due to absorption of moisture or is flexed due to change of temperature. When this occurs, the configuration of the outer circumferential surface of the housing may be changed to cause such an event that the base device is caught by the outer circumferential surface of the tool unit when the tool unit is moved to slide relative to the base device. In such a case, the tool unit may not be smoothly slid.
On the other hand, the housing may be formed of metal in order to enable the base device to clamp uniformly around the outer circumferential surface of the housing. The metal housing may not be easily deformed as in the case of the resin housing when the base device clamps the housing. Therefore, the outer circumferential surface of the housing can be uniformly clamped. However, in the case of the metal housing, it is difficult to ensure insulation of the drive motor and the other electric components disposed within the housing.
Therefore, there has been a need in the art for a power tool that can ensure insulation of electric components disposed within a housing and can keep accuracy in size or configuration of an outer circumferential surface of the housing.